Hi, thanks for the replies. I could put a nice piece of bogwood in the center, but for that I'd have to uproot the Echinodorus Ozelot(s) to make space. They have really really deep roots, and pulling them out is almost impossible. Besides, I have shells in my substrate, so I don't want to put more effort in this tank. Hopefully I'll upgrade to a larger tank in a year or so.
I used to inject CO2, the yeast method, but I have to make a new mixture now, and I'm just too lazy to do it. I use a PMDD mixture for fertilization. Its a 23 gallon tank.
Edit: Forgot to mention, my fishes are 4 serpae tetras and 3 widow tetras.